feat: specify module directory using swift_default_module_name directive (#566)

This allows a client to define the location where `swift_library` and
`swift_test` declarations should be written.

Also, this PR updates two of the examples to use this new feature.

Author: cgrindel

examples/firebase_example/crashlytics/BUILD.bazel

@@ -3,10 +3,8 @@ load("@build_bazel_rules_apple//apple:ios.bzl", "ios_application")
 load("@build_bazel_rules_apple//apple:macos.bzl", "macos_application")
 load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
 
-# Exclude this entire directory from having anything generated by Gazelle. That
-# way the test cases won't be fixed by `bazel run //:update_build_files` when
-# run in this repository.
-# gazelle:exclude **
+# gazelle:swift_default_module_name CrashlyticsSwiftUIExample
+# gazelle:exclude Shared/UITests.swift
 
 swift_library(
     name = "CrashlyticsSwiftUIExample",

examples/snapkit_example/BUILD.bazel

@@ -18,10 +18,6 @@ tidy(
 # Ignore the Swift build folder
 # gazelle:exclude .build
 
-# The example code has a strange layout. Do not generate swift_xxx for this
-# example.
-# gazelle:exclude **
-
 gazelle_binary(
     name = "gazelle_bin",
     languages = [
@@ -42,6 +38,8 @@ swift_update_packages(
     update_bzlmod_stanzas = True,
 )
 
+# gazelle:swift_default_module_name SnapkitExample
+
 swift_library(
     name = "SnapkitExample",
     srcs = [

gazelle/generate.go

@@ -42,7 +42,7 @@ func genRulesFromSrcFiles(sc *swiftcfg.SwiftConfig, args language.GenerateArgs)
 
 	// Be sure to use args.Rel when determining whether this is a module directory. We do not want
 	// to check directories that are outside of the workspace.
-	moduleDir := swift.ModuleDir(args.Rel)
+	moduleDir := swift.ModuleDir(sc.ConfigModulePaths(), args.Rel)
 	if args.Rel != moduleDir {
 		relDir, err := filepath.Rel(moduleDir, args.Rel)
 		if err != nil {

gazelle/internal/swift/module_dir.go

@@ -1,6 +1,11 @@
 package swift
 
-import "github.com/cgrindel/rules_swift_package_manager/gazelle/internal/pathdistance"
+import (
+	"path/filepath"
+	"strings"
+
+	"github.com/cgrindel/rules_swift_package_manager/gazelle/internal/pathdistance"
+)
 
 var moduleParentDirNames = []string{
 	"Sources",
@@ -9,7 +14,22 @@ var moduleParentDirNames = []string{
 }
 
 // ModuleDir returns the module root directory.
-func ModuleDir(path string) string {
+// The configModPaths is a list of relative paths to module directories defined by
+// swift_default_module_name directives.
+func ModuleDir(configModPaths []string, path string) string {
+	// Check if the path is a child of any of the directive paths
+	for _, modPath := range configModPaths {
+		// If modPath is empty string, then the module is set at the root of the workspace. So
+		// everything under the workspace is in this module.
+		if modPath == "" || modPath == path {
+			return modPath
+		}
+		modPathWithSlash := modPath + string(filepath.Separator)
+		if strings.HasPrefix(path, modPathWithSlash) {
+			return modPath
+		}
+	}
+
 	// If we do not see the module parent in the path, we could be a Swift module
 	moduleParentDistance := pathdistance.DistanceFrom(moduleParentDirNames, path)
 	switch moduleParentDistance {

gazelle/internal/swift/module_dir_test.go

@@ -9,18 +9,63 @@ import (
 
 func TestModuleRootDir(t *testing.T) {
 	tests := []struct {
-		path string
-		wval string
+		msg       string
+		cModPaths []string
+		path      string
+		wval      string
 	}{
-		{path: "Sources/Chicken", wval: "Sources/Chicken"},
-		{path: "foo/Source/Chicken", wval: "foo/Source/Chicken"},
-		{path: "foo/Sources/Chicken/Panther", wval: "foo/Sources/Chicken"},
-		{path: "Tests/ChickenTests/PantherTests", wval: "Tests/ChickenTests"},
-		// path does not contain module directory
-		{path: "foo/Chicken", wval: "foo/Chicken"},
+		{
+			msg:  "path is module, Sources at root",
+			path: "Sources/Chicken",
+			wval: "Sources/Chicken",
+		},
+		{
+			msg:  "path is module, Sources in sub-dir",
+			path: "foo/Source/Chicken",
+			wval: "foo/Source/Chicken",
+		},
+		{
+			msg:  "path is under a module path",
+			path: "foo/Sources/Chicken/Panther",
+			wval: "foo/Sources/Chicken",
+		},
+		{
+			msg:  "path is under a test module path",
+			path: "Tests/ChickenTests/PantherTests",
+			wval: "Tests/ChickenTests",
+		},
+		{
+			msg:  "path does not contain module directory",
+			path: "foo/Chicken",
+			wval: "foo/Chicken",
+		},
+		{
+			msg:       "path is module, config module paths provided",
+			cModPaths: []string{"foo", "bar"},
+			path:      "Sources/Chicken",
+			wval:      "Sources/Chicken",
+		},
+		{
+			msg:       "path is under config module path",
+			cModPaths: []string{"foo", "bar"},
+			path:      "foo/Chicken",
+			wval:      "foo",
+		},
+		{
+			msg:       "path is not a child of standard module dir, not in config module paths",
+			cModPaths: []string{"bar"},
+			path:      "foo/Chicken",
+			wval:      "foo/Chicken",
+		},
+		{
+			msg:       "module path is set to root of the workspace",
+			cModPaths: []string{""},
+			path:      "foo/Chicken",
+			wval:      "",
+		},
 	}
 	for _, tc := range tests {
-		actual := swift.ModuleDir(tc.path)
-		assert.Equal(t, tc.wval, actual)
+		actual := swift.ModuleDir(tc.cModPaths, tc.path)
+		assert.Equal(t, tc.wval, actual, tc.msg)
 	}
 }

gazelle/internal/swiftcfg/swift_config.go

@@ -3,6 +3,7 @@ package swiftcfg
 import (
 	"errors"
 	"os"
+	"sort"
 
 	"github.com/bazelbuild/bazel-gazelle/config"
 	"github.com/bazelbuild/bazel-gazelle/language"
@@ -61,6 +62,20 @@ func NewSwiftConfig() *SwiftConfig {
 	}
 }
 
+func (sc *SwiftConfig) ConfigModulePaths() []string {
+	dmnLen := len(sc.DefaultModuleNames)
+	if dmnLen == 0 {
+		return nil
+	}
+	modPaths := make([]string, 0, dmnLen)
+	for modPath := range sc.DefaultModuleNames {
+		modPaths = append(modPaths, modPath)
+	}
+	// Ensure that the results are consistent
+	sort.Strings(modPaths)
+	return modPaths
+}
+
 // SwiftBin returns the Swift binary.
 func (sc *SwiftConfig) SwiftBin() *swiftbin.SwiftBin {
 	if sc.SwiftBinPath == "" {

gazelle/internal/swiftcfg/swift_config_test.go

@@ -78,3 +78,34 @@ func TestWriteAndReadDependencyIndex(t *testing.T) {
 	// Ensure that the indexes are that same
 	assert.Equal(t, origsc.DependencyIndex, newsc.DependencyIndex)
 }
+
+func TestConfigModulePaths(t *testing.T) {
+	tests := []struct {
+		msg string
+		dmn map[string]string
+		exp []string
+	}{
+		{
+			msg: "no default module names",
+			dmn: nil,
+			exp: nil,
+		},
+		{
+			msg: "with default module names",
+			dmn: map[string]string{
+				"path/to/foo": "Foo",
+				"bar":         "Bar",
+			},
+			exp: []string{
+				"bar",
+				"path/to/foo",
+			},
+		},
+	}
+	for _, tt := range tests {
+		sc := swiftcfg.NewSwiftConfig()
+		sc.DefaultModuleNames = tt.dmn
+		actual := sc.ConfigModulePaths()
+		assert.Equal(t, tt.exp, actual, tt.msg)
+	}
+}